Solenoids consist of an electromagnetically inductive coil, wound around a movable armature. The coil is shaped such that the armature can be moved in and out of a center, altering the coil's inductance and thereby becoming an electromagnet. The force applied to the armature moves the armature in a direction that increases the coil's inductance, and a spring element within the solenoid resists the force generated by the magnetic field, and biases the push rod towards its original position.
Solenoids may be controlled directly by a circuit, and may have very low reaction times. Solenoids are used in many applications. For instance, a solenoid armature may be used to provide a mechanical force to some mechanism, such as controlling a pneumatic valve. Additionally, solenoid valves may be used to control the flow of various fluids.
A conventional solenoid force measurement system relies on fixed air-gaps. Adjusting the size of the air-gap adjusts the amount of magnetic flux detected during the solenoid operation and thus the air-gap must be precisely calibrated during a force measurement. To adjust the size of the air-gaps in a convention solenoid force measurement system, spacers (e.g., metal shims) are added between an upper and lower plate of the conventional solenoid force measurement system.
However, setting an air-gap with spacers is a time consuming and inaccurate procedure. Erroneous measurements are common in the conventional system, because the parallelism and flatness of the spacers often cannot be set to within high precision tolerance levels (e.g., +/−5 microns).